(1) Field of the Invention
The present invention relates to a liquid crystal display device, and in particular, to a so-called IPS (in-plane switching) system active matrix type liquid crystal display device.
(2) Related Art Statement
Active matrix type liquid crystal display devices are provided with a number of gate signal lines which extend in the direction x and are aligned in the direction y, and a number of drain signal lines which extend in the direction y and are aligned in the direction x on the surface of one of a pair of substrates provided so as to face each other with liquid crystal in between on the liquid crystal side, and have regions surrounded by a pair of adjacent gate signal lines and a pair of adjacent drain signal lines as pixel regions.
Each pixel region is provided with a thin film transistor which is turned on by a scanning signal coming from one gate signal line, and a pixel electrode to which a video signal is supplied from one drain signal line via the thin film transistor that is turned on.
In addition, IPS system liquid crystal display devices are formed so that the other electrode (counter electrode) which makes a pair with the above described pixel electrode is formed on the surface on the substrate side where the pixel electrode is formed, and liquid crystal is driven between the pixel electrode and the counter electrode by means of an electrical field which includes a component parallel to the surface of the above described substrate (in some cases referred to as lateral electrical field system).
In addition, liquid crystal displays where counter electrodes are formed of a transparent conductive film covering the surface at the center of each pixel, but not a thin strip in the periphery, and the pixel electrodes are formed of a transparent conductive film having a number of slits which faces each counter electrode with an insulating film in between on the counter electrode, and as a result, the opening ratio of the pixels is much higher, are known.
In this case, the counter electrodes are formed on the substrate in the same layer as counter voltage signal lines and connected to the counter voltage signal lines, and thus electrically connected to the counter voltage signal lines.
The counter voltage signal lines are formed of the same material as the above described gate signal lines, and a metal material is usually used. As a result, a reference signal which becomes a reference for a video signal can be supplied to the counter electrodes via the above described counter electrode signal lines having a low electrical resistance.
The following Patent Document 1, for example, discloses a liquid crystal display device having such a configuration.
(Patent Document 1) Japanese Unexamined Patent Publication 2005-284304